1. Field of the Invention
This invention relates to an apparatus for inspecting a bottom border portion (a circumferential corner portion of the bottom and a portion around the circumferential corner portion) of a transparent glass vessel to check whether or not a foreign article is present in the glass material of the bottom border portion. It is to be noted that, in the present specification, the terminology "transparent glass vessel" is intended to include not only literal transparent glass vessels but also translucent glass vessels and may be colorless or colored.
2. Description of the Related Art
Apparatus for inspecting a glass vessel for a foreign article which are used popularly are roughly divided into two types including an inspection apparatus which is used to principally inspect a body portion of a vessel and includes a diffusion light source and a solid state image pickup element camera arranged in a horizontally opposing relationship to each other with a vessel as an object for inspection interposed between them and another inspection apparatus which is used to principally inspect a bottom portion of a vessel and includes a diffusion light source and a solid state image pickup element camera arranged in a vertically opposing relationship to each other with a vessel as an object for inspection interposed between them.
However, It is actually difficult to inspect a bottom border portion of a glass vessel using an inspection apparatus of the horizontal arrangement type since, at a bottom portion of a vessel, the light path along which light from a light source passes through the glass material is comparatively long and attenuation of the light there is so great that, if the bottom portion is curved, then the light cannot pass through it due to refraction there.
Meanwhile, with an inspection apparatus of the vertical arrangement type, a bottom portion of a vessel is imaged by a camera through a mouth portion of the vessel. However, it is difficult to inspect a bottom border portion (a bottom circumferential corner portion and around such portion) due to reflection of light at an inner wall face of the vessel or refraction of light caused by a variation in shape, and particularly for a vessel having a small mouth, since the field of view of the camera to the bottom portion of the vessel is narrowed by the small mouth, a bottom circumferential corner portion cannot be inspected with the inspection apparatus of the vertical arrangement type.
By the way, cullet (fragments of glass) collected from the city is recycled as a raw material for glass vessels as a part of recycling of glass vessels. However, such cullet collected from the city normally contains a large amount of substances, for example, pottery, porcelain, metals such as aluminum, and heat resisting glass other than a raw material of glass for glass vessels to be recycled, and therefore, it is tried to remove such substances to the utmost. However, since they cannot be removed completely, they remain as foreign articles in a glass vessel as a product.
Where such foreign articles are present in a body portion or a bottom portion of a glass vessel, they can be found out almost by an inspection apparatus of the horizontal type or the vertical type described above, and accordingly, particularly at a content filling step after shipment of products of glass vessels, an accident of breakage caused by a foreign article present in a bottom portion or a bottom portion of a glass vessel seldom occurs. However, since a foreign article in a bottom border portion of a glass vessel cannot be found out with a conventional inspection apparatus as described hereinabove, although the bottom border portion has a greater thickness of material than the other portions of the glass vessel, it is a situation at present that accidents of breakage at the bottom border portion arising from presence of a foreign article there increase as the amount of use of collected cullet increases.